Embodiments of the invention relate to conductive interconnect structures and methods for forming conductive interconnect structures.
In electrical assemblies such as multichip modules, integrated circuit chips are electrically coupled to a circuit substrate through one or more interconnect structures. These interconnect structures provide electrical pathways between the chip and the circuit substrate. For example, interconnect structures such as conductive posts can be disposed between a chip and a circuit substrate to electrically communicate the chip and the substrate.
If plural interconnect structures are disposed between a chip and a circuit substrate, at least one end of each interconnect structure is soldered to the chip or the circuit substrate. The steps used in a typical soldering process include fluxing, reflowing, and post-solder cleaning. After solder paste is applied to the surfaces to be joined, a flux in the solder paste removes metal oxides (fluxes) from the solder particles in the solder paste and from the surfaces to be soldered. Removing oxides is desirable, because metal oxides typically increase the resistance of the formed solder joint and decrease the wettability of the solder. During reflow, the solder paste is heated and the solder particles coalesce into a cohesive solder body. The solder body joins the surfaces to be soldered so that they are in electrical communication with each other. After reflow, flux residue generated during the fluxing step is removed in the post-solder cleaning step. In a typical post-solder cleaning step, a solvent is applied to the solder joint to remove flux residue from the solder joint.
Fluxing has generally been effective to form interconnections between a chip and a circuit substrate. However, fluxing increases the number of steps used in the interconnection process. This consequently increases the cost of producing the intended product. Moreover, many solvents used in the post-solder cleaning step, are not environmentally friendly. In view of these problems, it would be desirable to provide for interconnect structures which can potentially decrease or eliminate fluxing steps in an interconnection process.
Embodiments of the invention are directed to interconnect structures and methods of making and using interconnect structures.
One embodiment of the invention is directed to a conductive post comprising: a tapered first end portion having a first substantially planar surface and a concave surface adjacent to the first planar surface, a second end portion including a second substantially planar surface, wherein the second planar surface has a larger area than the first planar surface; and an intermediate portion disposed between the first end portion and the second end portion.
Another embodiment of the invention is directed to a method for forming a conductive interconnect structure, the method comprising: forming a conductive body on a conductive region, wherein a first end portion of the conductive body is disposed distal to the conductive region and a second end portion of the conductive body is disposed proximate the conductive region; and removing conductive material from the first end portion of the conductive body such that the first end portion is tapered.
Another embodiment of the invention is directed a method comprising forming an electrically conductive article comprising a dielectric layer, a conductive region on the dielectric layer, and a conductive post on the conductive region, wherein a tapered first end portion, of the conductive post is distal to the conductive region, and a second end portion of the conductive post is proximate to the conductive region; and inserting at least a portion of the tapered first end portion into a solder body, wherein the tapered first end portion is in electrical communication with an interior region of the solder body.
These and other embodiments of the invention are described in further detail below.